Centrifugal pump impeller



Dec. 27, 1966 L. DENIS 3,29

CENTRIFUGAL PUMP IMPELLER Filed March 18, 1964 2 Sheets-Sheet 1INVENTOR. Lours 05; N16.

ZTTOEw/Sf Dec. 27, 1966 L. DENIS 3,294,027

CENTRIFUGAL PUMP IMPELLER Filed March 18, 1964 2 Sheets-Sheet 2 INVENTORLOUIS DENIS United States Patent 9 Claims. (or. 103-115 This inventionrelates to centrifugal pumps, compressors, superchargers and likeapparatus and more particularly to an impeller for such devices having arotary diffuser wherein the impeller blades are directly welded onto ahollow shaft.

In the field of rotary diffusers and impellers, it has been the generalpractice to construct such devices by fabricating a structure comprisedof a hub, a plurality of impeller blades mounted on said hub andenclosed within a disc and a shroud member and diffuser sections.Thereafter such structure as a unit was mounted on a solid shaft.Usually the disc and front shroud were hammered and machined in onepiece and welded onto the impeller blades.

In accordance with the conventional manner, the impellers were shrunkfitted onto the shaft, resulting in an expensive and laboriousoperation. Also the machinings of the various parts were numerous. Byway of example, the shaft and the hub were entirely machined separately;thereafter, the hub had to be machined again after the mounting thereofonto the shaft.

The solid shaft had to be designed to accommodate the weight of theimpeller and its own weight. This led to very large shaft diameters andto disadvantages from the aerodynamics point of view because of the areaoccupied by the shaft and hub in the inlet.

The rotary diffuster impeller of the present invention as hereinafterdescribed obviates such disadvantages by employing a hollow shaft andfurther, by attaching the impeller blades directly onto such hollowshaft, thereby eliminating the hub.

It is therefore an object of the present invention to provide a new andimproved impeller for centrifugal pumps, compressors, superchargers andlike apparatus.

Another object of this invention is to provide a new and improvedimpeller of the rotary diffuser type for centrifugal apparatus which issimple in construction, reduced in weight, reliable in operation andeasy to manufacture.

A specific object of the present invention is to provide a new andimproved impeller of the rotary diffuser type which is provided with ahollow shaft for obtaining impellers lighter than the conventional onesoperative at the same critical speed.

Still another specific object of the present invention is to provide anew and improved impeller of the rotary diffuser type having a hollowshaft and wherein the impeller blades are directly attached to suchhollow shaft for precluding the necessity of a hub.

These and other objects and advantages of this invention will becomereadily apparent upon consideration of the following description anddrawings in which:

FIGURE 1 is an axial sectional view of a rotary diffuser having an oddnumber of impeller blades constructed in accordance with the principlesof this invention;

FIGURE 2 is an axial sectional view of a rotary diffuser constructed inthe conventional known manner;

FIGURE 3 is an axial sectional view of another embodiment of the rotarydiffuser taken adjacent the impeller blades.

FIGURE 4 is an axial sectional view of a modified hollow shaft having aprestressed rod therein; and

FIGURE 5 is a composite illustration showing a further embodiment of thehollow shaft in axial section and in end elevation.

Referring to the drawings and particularly to FIGURE 2, it will be notedthat a rotary diffuser constructed in accordance with the knownconventional manner comprises a solid rotatable shaft 2 journalled atits outer ends respectively in suitable bearings 4 and 6. A hub 8 isrigidly secured onto shaft 2 as for example by shrink fit ting. Sincethe right side of the construction shown in FIGURE 2 is identitxil tothe left side and symmetrical thereto about a plane passing through theline indicated as A-A normal to the axis of shaft 2, only the right sidewill be described. Rigidly secured on hub 8 as for example by weldingare a plurality of impeller blades 10 enclosed between disc 12 and outershroud member 14. The impeller blades 1f extend from the radially inwardedges of disc 12 and outer shroud member 14 respectively and terminatein outer end portions 16. Portions 18 and 20 of disc member 12 and outershroud member 14, respectively, extend outwardly beyond the outer endportions 16 of blade members 10 and are slightly axially divergent toform a rotary diffuser.

In FIGURE 1 there is shown a rotary diffuser constructed according tothe principles of this invention comprising a hollow shaft 22 havingreduced end portions 24 and 26 journalled in bearings 28 and 30respectively. Shaft 22 is rotated by a power means (not shown) in amanner well known in the art.

Directly attached to the rotatable hollow shaft 22 as for example bywelding are a plurality of flat impeller blades 32 which are equallycircumferentially spaced about hollow shaft 22. As in the case of FIG.2, only the right side of the structure shown in FIG. 1 will bedescribed since it is identical and bilaterally symmetrical to the leftside. A disc segment 34- and a shroud segment 36 are disposed-betweeneach circumferentially successive pair of blades 32 and are rigidlysecured thereto as for example by welding to form an inner and outershroud, respectively. The segments 34 and 36 have coaxial surfaces ofrevolution and outer peripheries 38 of equal radius. Impeller blades 32extend from the periphery of hollow shaft 22 and terminate in outer endportions 40 substantially inwardly from the outer periphery 38 of segments 34 and 36. Portions 42, 44 of the segments 34 and 36 respectivelyextend outwardly beyond the outer end portions 40* of the impellerblades 32 and are preferably slightly axially divergent to form a rotarydiffuser. Portions of the segments 34 and 36 nearest to the hollow shaft22 are radially spaced to form an inlet opening 46. The rotatable hollowshaft 22 is rotated by power means (not shown) in a manner well known inthe art.

In operation of this device the shaft along with the impeller mountedthereon is rotated at a predetermined speed within a suitable impellercasing in a manner well known in the art. Such casing is so designedthat a suitable supply of air is available at the inlet opening 46between each pair of blades and a suitable path for exit of the air fromthe impeller is provided adjacent the outer periphery 38. It is readilyapparent that in eliminating the hub by attaching the blades directlyonto the shaft as in the present invention while maintaining the samebasic dimensions of the inlet opening as in the case of an impellerhaving a hub, an increase of How area of the inlet is obtained.

Another advantage residing in the use of an impeller of this inventionis apparent in obtaining impellers lighter than the conventional onesfor the same critical speed design. Accordingly, an appreciablereduction in weight and cost is realized. Moreover, the reduction inweight lightens the loads on the bearings and stands, thereby resultingin a longer life span of these elements. Furtheri more, the eliminationof the massive hub and the elimination of weight within the shaft properresults in a reduction of WR or WK in the total rotatingdassembly wherexensive motors can be employe s fi ll an other advantage obtained in theimpeller of th present invention is due to the utilization of a hollowshaft which is more rigid than a solid shaft because its area of momentof inertia increases at a greater rate than shaft weight. Thus, it has agreater ratio of moment of inertia to shaft weight than a solid shaft ofthe same i er. ii i urther advantage residing in the impeller of thlsinvention is that during the fabrication of the instant 1mpeller, theshaft may be preheated internally to facilitate the blade weldingprocess. In service, the hollow shaft design maintains cooler operatingtemperatures in the area of both the impeller and the bearing journalswhich is a particularly desirable feature when handling hot ses. Anadditional advantage in eliminating the hub is obtained in applicationswhere the rotor is subjected to large temperature changes in a shorttime interval, such as on start-up by way of example, in theconventional devices whereby the hub is heated at a faster rate than theshaft. This condition creates a looseness between the hub and shaft,resulting in a temporary unbalance of the rotor as sembly. Of course, byeliminating the hub, such condition is precluded.

Still a further advantage resides in fabricating the shrouds insegments, thus resulting in a substantial cost reduction as compared tothose shrouds formed by hammering and machining.

FIG. 3 shows another embodiment of the impeller of this inventioncomprising a circular disc 48 having a central, circular opening 50therethrough for receiving a hollow shaft 22'. Disc 48 is suitably,rigidly attached to the hollow shaft 22 as by means of welding. Aportion of the disc near its periphery is tapered radially outwardly toform inner walls 52 and 54 of a double inlet rotary diff-user.

The embodiment of FIG. 3 has an advantage over the embodiment firstdescribed in that a single disc member 48 is effectively employed toprovide inner walls or shroud members for a double inlet rotarydiffuser, thus facilitating the fabrication thereof and providingstrength without reducing the flow area of the respective inlets.

FIG. 4 illustrates a second embodiment of the hollow shaft of thepresent invention comprising a constant diameter hollow shaft 22".Elongated tip members 56 and 58 extend axially outwardly from theopposite ends of shaft 22" and have central axial bores 60 and 62respectively, extending longitudinally therethrough. Tip members 56 and58 are provided with circular flanges 64 and 66 respectively concentricwith tip members 56 and 58 respectively, for abuttingly engaging theopposite end faces of shaft 22". An elongated metallic prestressedmember 68 extending along the longitudinal axis of shaft 22" is receivedin bores 60 and 62 respectively and is provided with threads at itsopposite end portions. Internally threaded nuts 70 are adjustably,releasably secured to the opposite end portions of prestressed member68. Such an arrangement not only effectively secures the tip members 56and 58 to the constant diameter hollow shaft 22", but also provides theadded advantage of employing the prestressed member for influencingstresses acting on the hollow shaft of the impeller.

FIG. shows another embodiment of the hollow shaft of the presentinvention comprising a constant diameter shaft 22" having its oppositeend portions journalled in bearings 72 and 74 respectively. Each of thebearings comprises six rollers 76 arranged in two rows of three rollerseach, having their axes of rotation lying in a comrnon horizontal planeparallel to and located below the longitudinal axis of shaft 22'. Withthis arrangement,

one of the rollers can be removed and replaced while the other rollerseffectively support shaft 22".

Although a double inlet centrifugal impeller has been shown anddescribed, it should be realized that a single inlet centrifugalimpeller could be constructed in accordance with the principles of thepresent invention.

Preferred embodiments of this invention having been described andillustrated, it is to be realized that modifications thereof may be madewithout departing from the broad spirit and scope of this invention.Accordingly, it is respectfully requested that this invention beinterpreted as broadly as possible and be limited only by the prior art.

I claim:

1. A centrifugal pump rotor-impeller assembly comprising: an elongatedhollow shaft rotatable about its longitudinal axis and supported forsuch rotation at longitudinally spaced journal portions thereof; aplurality of blades having forward, rearward, outer end, and inner endportions, said blades being rigidly secured at their inner end portionsto said shaft and extending outwardly in spaced relationship from acircumferential section of said shaft; disc means rigidly secured withrespect to said shaft and extending peripherally thereabout in abuttingrelationship with a substantial radial expanse of the rearward portionsof said blades, said disc means being an integral continuous member; anda shroud comprised of shroud segment means extending between the forwardportions of adjacent pairs of blades and spaced from said disc means andsaid shaft to define generally radially outwardly directed passagewayshaving generally axially facing inlets and radially outwardly facingoutlets adjacent the outer end portions of said blades.

2. A centrifugal pump rotor-impeller as set forth in claim 1 whereineach of said shroud segments is rigidly secured to at least one blade ofsaid Pair of blades.

3. A centrifugal pump rotor-impeller assembly as set forth in claim 1wherein said blades and said disc means are rigidly secured by welding.

4. A centrifugal pump rotor-impeller assembly as set forth in claim 1wherein said shroud segments means are secured by welding.

5. A centrifugal pump rotor-impeller assembly comprising: an elongatedhollow shaft rotatable about its longitudinal axis and supported forsuch rotation at longitudinally spaced journal portions thereof; aplurality of blades having forward, rearward, outer end, and inner endportions, said blades being rigidly secured at their inner end portionsto said shaft and extending outwardly in spaced relationship from acircumferential section of said shaft; disc means rigidly secured withrespect to said shaft and extending peripherally thereabout in abuttingrelationship with a substantial radial expanse of the rearward portionsof said blades; a shroud comprised of shroud segments extending betweenthe forward portions of adjacent pairs of blades and spaced from saiddisc means and said shaft to define generally radially outwardlydirected passageways having generally axially facing inlets and radiallyoutwardly facing outlets adjacent the outer end portions of said blades;and an elongated prestressed member within said shaft, said prestressedmember extending longitudinally substantially end-to-end of said shaftand being supported within said shaft to exert a stress on said shaftdirected from the ends of said prestressed member toward said blades.

6. A centrifugal pump rotor-impeller assembly as set forth in claim 5wherein said disc means is comprised of segments extending between therearward. portions of pairs of adjacent blades, each of said discsegments being rigidly secured to at least one blade of said pair ofblades.

7. A centrifugal pump rotor-impeller assembly as set forth in claim 5wherein each of said shroud segment means is rigidly secured to at leastone blade of said pair of blades.

5 8. A centrifugal pump rotor-impeller assembly as set forth in claim 5wherein said blades and said disc means are rigidly secured by Welding.

9. A centrifugal pump rotor-impeller assembly as set forth in claim 5wherein said shroud means are secured by welding.

References Cited by the Examiner UNITED STATES PATENTS 1,953,064 5/1934Dowson 103-115 2,337,619 12/1943 Miller 230134 2,344,444 3/ 1944Malczewski 230--134 2,402,204 6/ 1945 Phelan et a1. 103115 2,443,4116/1948 Wolfe 230134 2,697,589 12/1954 Davey 1031 15 6 10/1957 Wagner eta1. 29156.8 6/ 1962 Kaplan 25 3-78 1/1963 Kroeckel 29-1568 2/1963 Clarke230-134 10/1963 Clarke et a1 103-115 6/ 1964 Lindquist 230134 1/ 1965Szewalski et al 253-78 FOREIGN PATENTS 2/ 1948 France. 3/ 1932 Germany.4/ 195 6 Germany. 11/ 1949 Great Britain.

MARK NEWMAN, Primary Examiner.

HENRY F. RADUAZO, Examiner.

1. A CENTRIFUGAL PUMP ROTOR-IMPELLER ASSEMBLY COMPRISING: AN ELONGATEDHOLLOW SHAFT ROTATABLE ABOUT ITS LONGITUDINAL AXIS AND SUPPORTED FORSUCH ROTATION AT LONGITUDINALLY SPACED JOURNAL PORTIONS THEREOF; APLURALITY OF BLADES HAVING FORWARD, REARWARD, OUTER END, AND INNER ENDPORTIONS, SAID BLADES BEING RIGIDLY SECURED AT THEIR INNER END PORTIONSTO SAID SHAFT AND EXTENDING OUTWARDLY IN SPACED RELATIONSHIP FROM ACIRCUMFERENTIAL SECTION OF SAID SHAFT; DISC MEANS RIGIDLY SECURED WITHRESPEC TO SAID SHAFT AND EXTENDING PERIPHERALLY THEREABOUT IN ABUTTINGRELATIONSHIP WITH A SUBSTANTIAL RADIAL EXPANSE OF THE REARWARD PORTIONSOF SAID BLADES, SAID DISC MEANS BEING AN INTEGRAL CONTINUOUS MEMBER; ANDA SHROUD COMPRISED OF SHROUD SEGMENT MEANS EXTENDING BETWEEN THE FORWARDPORTIONS OF ADJACENT PAIRS OF BLADES AND SPACED FROM SAID DISC MEANS ANDSAID SHAFT TO DEFINE GENERALLY RADIALLY OUTWARDLY DIRECTED PASSAGEWAYSHAVING GENERALLY AXIALLY FACING INLETS AND RADIALLY OUTWARDLY FACINGOUTLETS ADJACENT THE OUTER END PORTIONS OF SAID BLADES.